The last enclave of pagan tribespeople in remotest Pakistan might already have fallen to the combined ravages of modernity and militant Islam were it not for a redoubtable, eccentric Englishwoman.

The journey to Birir in the North-West Frontier Province of Pakistan takes you along a terrifying jeep track of 11 hairpin miles. It winds so sharply and narrowly that you can’t see more than 100 yards ahead; only extremely skilful drivers can handle the challenge of its crumbling steepness, and every year many people are killed as Jeeps overloaded with timber or passengers or both slide off the edge.

Birir and its two neighbouring valleys nestle below the soaring white walls of the Hindu Kush range, the last strongholds of the Kalash – the ‘wearers of black’. The Kalash are the surviving Kafirs of Kafiristan, the ‘land of the infidels’ made famous by Rudyard Kipling (and then the film director John Huston) in The Man Who Would Be King. For centuries, Kafiristan stretched across Afghanistan and Pakistan; today all that remains is a hill tribe of 3,500 – the only pagans to be found for thousands of miles in any direction.

Many of the Kalash claim descent from the armies of Alexander the Great, and indeed their faces do look strikingly similar to those you would encounter in Croatia or Montenegro. They make wine, revere animals and believe in mountaintop fairies. To observe their lives is to be transported far from today’s North-West Frontier, with its increasingly militant, misogynistic brand of Islam, to a world that Homer’s contemporaries might have recognised.

Polytheists who divide the world into male and female realms, the Kalash claim they were once a literate culture but their books were burnt long ago by savage tribes. Their religion harks back to ancient fertility cults. Some among them practise an annual rite known as ‘budalak’, when a teenage boy is selected to go alone into the high forests for almost a year. When he returns on a feast day, he may sleep with any and as many Kalash women as he chooses.

The Kalash have long been so isolated that they are believed by nearby peoples to hibernate like animals. But the rugged remoteness that once protected them is disappearing fast as better roads are built, and Muslim homesteaders from Punjab and elsewhere in Pakistan outnumber the Kalash. The settlers have brought with them mosques, missionaries and a money economy that has landed in deep debt families more familiar with the barter system. It is a familiar story.

With exposure to the electric world of mobile phones, videos and satellite television, the Kalash young yearn for the glamour of life beyond their valleys; and today the Kalash culture is under threat from militant Islam, rapid deforestation, technology and a lethal combination of gullibility and greed among the Kalash themselves. Indeed, it would probably be gone already, were it not for the efforts of an eccentric 69-year-old Englishwoman known locally as ‘Bibi Doe’.

For two decades Bibi Doe has raised money for inoculations, fresh-water pipes and bridges. She has driven sick people to the hospital in Chitral and distant Peshawar, where her little NGO paid the bills. It was she who built the first latrines here and brought the first stoves – with help from the British High Commission – so that the women would no longer suffer eye and lung diseases from open fires inside the houses. She opened dispensaries where locals can get aspirin and antibiotics that stop the children dying from fever.

It is hard to believe that anyone could make the journey from Peshawar to Chitral so often – but last October alone Bibi Doe did it 12 times. She regularly puts up with dangers and physical discomforts that would fell a woman half her age. In 1990, for instance, she almost drowned when her Land Cruiser was hit by a flash flood while crossing a river. (She never now wears a seatbelt.)

For Bibi Doe, death threats are a fact of life. She has battled corrupt officials, the frontier timber mafia, Kalash distillers of lethal moonshine liquor, bigoted mullahs, pimps, jihadist militants, insensitive tourists, unscrupulous entrepreneurs, giant aid agencies, foreign academics and do-gooders she considers exploitative. ‘If you ever read that I’ve died in accident,’ she said as we loaded up her Land Cruiser before leaving for Birir, ‘you’d better come back and investigate what really happened.’

Bibi Doe is named after her favourite Kalash dog – an orphaned pup she adopted in 1986 after its mother was taken by a wolf. The children of the valleys heard her shouting, ‘Bibi Doe! Bibi Doe!’ as she tramped up and down the trails with a backpack full of medicines. It became their name for her, and then everyone’s name for her. When she raised money for the repair of a 1927 suspension bridge across the Chitral river, on which the commerce of the valleys depends, she ensured that a plaque on the bridge read, ‘Repaired 2006 by Bibi Doe’.

Before she was adopted by a Kalash family in Birir in 1981, Bibi Doe was known as Maureen Lines. Born in north London to a middle-class family, Lines has over the years been a tourist official in Greece, a taxi driver, a waitress, a domestic in Beirut, a petrol pump attendant and a writer of Gothic novels. She has also written several books about her travels in Afghanistan and the North-West Frontier. Certainly, she never planned to become an aid worker. ‘Never in my wildest dreams did I think I’d be involved in development.’

We were in her little room in Birir, the fire blazing and a gas lamp hissing in the background. She explained that her first memories are of huddling in a Morrison shelter as bombs of the Blitz rained down. An only child (her father worked in radar), her companions growing up were dogs, books and fantasy. She left school at 16 and went to study shorthand and speech at Harrow Tech with hopes of becoming an actress or a journalist. Both dreams dissolved when her mother left her father.

Soon afterwards, Lines ran away and found a job as a waitress at one of the new espresso bars in central London. She then headed to Paris, to sell the Herald Tribune like Jean Seberg in A bout de souffle. In 1961 she emigrated to America. ‘It was one of those impulses. I’ve lived my life on impulses. I was standing at a bus stop in the rain, I’d had a fight with my lover and I was out of work when I saw a sign advertising for “domestics in America”. Six months later I was on a ship to New York.’

The job didn’t last long and Lines went to work in a coffee shop in Greenwich Village. The beatnik years were in full swing, and for a decade she worked just to pay for partying and studying. First she went to the New School to study journalism and poetry, and then switched to New York University to do international affairs and Arabic. There, she discovered her love of travel and of the Muslim and Arab worlds. In 1964 – before the advent of overland holidays and the hippie trail to India – she hitchhiked from Istanbul to Damascus. ‘Everyone said I was a fool and that I’d be murdered or raped. But I never had a problem as a woman,’ she said.

Lines had moved back to England when her travels took her to Pakistan and the Kalash valleys for the first time in 1980. It was the end of a voyage taking in Cairo, Khartoum and Bahrain. She and Pakistan got on well immediately. ‘Within 24 hours I was on the radio giving my impressions of the country,’ she said with a laugh. ‘It’s been like that ever since.’

Her first contact with a Kalash woman came when Lines was trying to find a route across a fast-flowing stream. A tall, dignified woman – wearing a veil, which was unusual – showed her a place to cross. On her way across the smooth stones, Lines slipped. To her surprise the woman was right behind her and caught her arm. As she did so, her veil slipped and Lines saw that her face was disfigured by a mass of ‘pink and black scabs’. A few days later Lines went into Chitral and bought some medicines and took them back to treat the woman.

A year later, she returned to the valleys and managed to secure a permit to stay for a month. It was then that she met Tak-Dira, who adopted Lines and became her ‘Kalash mother’. It was during this second stay that Lines resolved to go back to America to gain a medical qualification so she could help the Kalash.

Back in New York she trained as a paramedic, though illness delayed her return to the valleys for four years. Once established, she became a kind of barefoot doctor in hiking boots walking from one village to another, a backpack full of medicine, a dog or two at her side. ‘I did 10 to 12 miles a day. I had a ball.’ Whenever she could, she ‘would literally hijack passing doctors’ for medicines.

In 1990 she started her pit latrine and stove projects. The first money she raised came from bake sales and the like at her late mother’s home in Princes Risborough in Buckinghamshire. But soon she began to raise money from governments and embassies. She found herself spending more and more time in Islamabad talking to diplomats and Pakistani officials, and getting more involved with environmental threats to the Kalash, such as uncontrolled tourism and deforestation.

Three years later, she started her Pakistani NGO, the Kalash Environmental Protection Society (Keps) – and then, in 1995, the British charity that supports it, the Hindu Kush Conservation Association. She became a citizen of Pakistan after one of her ‘enemies’ in officialdom almost managed to get her deported a few years ago. ‘This young man married me and that’s how I got my ID card,’ she said. ‘He’s somewhere in England now, I don’t know where.’

I had first met Maureen Lines in Chitral in 1994. She had just founded the ‘Kalash Guides’ to soften the impact of tourism in the valleys. Travellers were encouraged to use the local guides she had trained rather than outsiders from the hotels of Chitral. Lines had had enough of seeing ‘Jeeps tear up people’s fields’ and busloads of tourists surrounding Kalash women as they bathed in the river. The scheme also meant that Kalash families rather than Punjabi carpetbaggers gained some economic benefit from tourism, and ensured that visitors didn’t get lost on the mountain trails. I stayed in a guest room of one of the guides in Birir – a fascinating but cold and flea-ridden experiment in medieval living. The guide scheme worked until 9/11 and the Afghan war, which dried up the tourist flood.

Today, Lines is as remarkable, thoughtful and energetic as when I last saw her. She is also tough, cantankerous, slightly deaf and marvellous company. Her no-nonsense approach seems to have neutralised the usual disadvantages of being a woman in one of the most sexually oppressive places in Asia. The North-West Frontier of Pakistan is the most conservative part of a conservative country. In the picturesque bazaars of Chitral town, you are unlikely ever to see a woman. Here, it is said that a woman goes out in public twice in her life: once to leave her father’s house for her husband’s, the next time to be buried. The contrast with the Kalash valleys could hardly be greater. The first thing you notice in Birir and its sister valleys is the sound and sight of women – ubiquitous, assertive and wearing traditional dress.

There are no hotels in the citadel villages of Birir so Lines invited me to stay with her Kalash family in a room next to their one-storey house, set against the hillside, with its rickety veranda looking down on a grove of trees surrounding a little cemetery. The flat-roofed houses are made of stone, wood and mud to withstand the region’s earthquakes. Extended families of 20 or more live together in each house, in a single dark room with an earthen floor.

In the house of Lines’s adoptive family, we huddle against the cold around the wood-burning metal stove. We are sitting on low stools made of walnut and animal hide. Lines had brought rice – too expensive for most Kalash – to make a feast, with cooked vegetables and flat bread and a salad of onions and tomatoes. We drank the rough homemade red wine, which tastes a bit like vodka and grape juice. As we ate, Lines chatted in Kalash to Sainusar, Tak-Dira’s daughter, in her midforties, and various other family members; a small bulb above us emitted a feeble glow. There is some electricity in the valley – from two small hydro-electric plants. Some of the men went off elsewhere to smoke hashish, a habit introduced by hippie backpackers. But everyone was in bed soon after nightfall.

The next morning, we visited one of Lines’s dispensaries in lower Birir. Unlike the government dispensary further up the valley, it is well stocked. One of the problems faced by the Kalash, like so many other remote people in the subcontinent, is that government facilities tend to exist only on paper or to suffer from extreme absenteeism. For instance, there is a government doctor assigned to the Kalash valleys, but he is rarely, if ever, there.

Lines’s dispensary is a bare concrete room with a couple of shelves of medications and a ledger. It is maintained by Hassan and Shah Hussein, two voluble young Muslim men from a nearby village. One is a Kalash convert, the other is from one of the families who have moved here from the Punjab and elsewhere in Pakistan.

One of the strange things about morning in Birir is the amplified sound of the muezzin’s call to prayer. Though the Pakistani federal government ‘genuinely supports freedom of religion’, as Lines said, and has long been serious about protecting the Kalash culture, the provincial government is now controlled by the Muslim Fundamentalist party, the MMA, which has strong links to the Taliban across the border, and which disapproves of the infidel presence in their midst.

According to Minocher ‘Minoo’ Bhandara, a Pakistani MP and former minister for minorities, Muslim families here insist that the families of Kalash brides or grooms also convert, so they don’t have to suffer the humiliation of Kafir in-laws. ‘A lot of money is exchanged, I believe,’ he said. ‘They don’t convert for any religious or ideological reason – there has to be a financial incentive.’

I spent a further week with Lines in Birir as she visited her various projects in the three valleys: an irrigation project here, a dispensary there, latrine projects everywhere. Though it was cold and she hated the way her knees and back limited her mobility (‘I’m worried I won’t be able to go up to the high pastures in the spring,’ she grumbled), she was ebullient after a successful fundraising dinner in Islamabad and positive meetings with the Kalash Co-ordinating Committee.

Stopping deforestation by what Lines calls ‘the timber mafia’ takes up an increasing amount of her time. There are very few forests left in Pakistan and there is enough demand to render the antideforestation laws virtually meaningless. Donkeys and overloaded Jeeps carry heavy loads of sweet-smelling cedar and deodar out of the valleys every night. As the forests disappear, flash floods become more and more common. ‘The majority of the people’ are behind her, Lines said. ‘But the big guys in Birir – corrupt Kalash and corrupt Muslims – they don’t give a damn. They’ve got enough money accumulated, they can go some place else after the land has been ruined. The other problem is corruption in the forest service. We had a good guy here but the bearded ones [the Taliban] had him transferred and the wood is now pouring out again.’

Two things ensure that Lines can punch above her weight. She has access to the Pakistani media and a network of supporters in Pakistan and abroad. Among those allies is the railways chief Shakil Durrani, who was the district commissioner in Chitral when Lines first moved to Pakistan, and then the chief secretary of the whole North-West Frontier Province. He found the Kalash fascinating and ‘wanted to do my bit to ensure that they remain, not as zoo people but a vibrant living people’. Like many other sympathetic observers, Durrani believes that the Kalash are ‘their own worst enemies’ with their lawsuits, squabbling disunity and what he calls ‘their casual attitude to many things in life, especially money.’ Durrani still does what he can to help and is on the board of Keps. At one point, he asked Diana, Princess of Wales, to become a patron of the Kalash. ‘She agreed in principle to lend her name,’ he told me, though she died before the project came to fruition.

A couple of days into our stay, all work – though not Lines’s – came to a halt. An old man had died. The funeral would last for three days, during which time people would walk from all of the valleys to pay their respects. Funerals are expensive for the Kalash, partly because work ceases, but mostly because the bereaved family is expected to sacrifice goats and cows to feed the guests. It is one of the only times that the Kalash eat meat; animals are too valuable to slaughter except on such occasions.

During the funeral, a group of Kalash women formed a semicircle around the corpse – which lay on a bier, covered in gold cloth – and linked arms. They danced around the body while others chanted. You could tell the women from the bereaved family because they were the only women with bare heads (a Kalash woman takes off her headdress only when in mourning). In between the dances, the male elders told the life story of the deceased in a kind of chant. It was an extraordinary spectacle.

After the funeral, I accompanied Lines to Bumburet, the largest and most beautiful of the Kalash valleys, with snow-clad peaks visible at both top and bottom. But there are grubby hotels here and shops and NGO offices, and even satellite dishes on some of the houses. Even with tourism so weak, there are more foreigners here than in the other valleys. When we stopped for tea and some flat bread and goat’s cheese, I met an Italian anthropology professor dressed in full shalwar kameez and Chitrali cap, his eyes made up with eyeliner.

Here, a wealthy Greek NGO is building a huge cedar-wood mansion they have called the Kalash House, which will include a museum, school and conference centre. I met Athanasios, the head of the NGO, briefly as he drove out of the valley in his SUV. He has shaggy hair and dark glasses and looks a bit like a 1970s rock star. Lines said that the mansion is ‘a monument to his egotism’. At one point, she told me, Athanasios gave what he called a ‘scholarship’ – in fact a cash gift of 30,000 rupees – to every Kalash family with a child of school age. ‘A cash gift. It was the most corrupting thing. Many of the families used the money to buy land.’

She talked a great deal about the ‘corruption’ of the Kalash. Sometimes she meant it in the literal sense. One of the wealthier Kalash families became so by stealing and selling statues in the valleys. She is greatly concerned by the replacement of the barter system, and the loss of traditional skills, such as shoemaking (the women now wear plastic shoes from Chitral that hurt their feet). Even the education offered here is not entirely a boon, in her opinion. ‘Some of the boys speak a few words of English, put on Western clothes and think “Man, I’m cool”. They have enough education not to want to work in the fields but not enough to get a job in the world outside.’ Education has also undermined the gerontocratic social system of the valleys: young people with a smattering of literacy despise their illiterate parents and long to join the exciting outside world.

Not everyone agrees with Lines that the Kalash culture should be protected from the outside world with its technology and subversive pop culture. Minoo Bhandara, one of Lines’s longtime supporters, is adamant that she is wrong about development in the valleys. As he told me in his office in Islamabad, ‘She doesn’t want hotels. She wants tough roads so people tough it out. She doesn’t want too many tourists to contaminate the Kalash. But they are like other ordinary folks: if you ask them what they want most in the world they would say, “a cell phone and a television”. The rest of the world has them, why not them?’

But Lines believes that sanitation and education should come before electricity and improved roads. ‘They need some knowledge and awareness first. I saw the same thing in Pathan culture when I first came to Pakistan,’ she said. ‘I was taken to a small village in the tribal areas and they had a refrigerator in the sitting-room but no sanitation, no drinking water, no toilet. They did have electricity.’

Lines is horrified by the money that has been wasted by big aid agencies here. I got some sense of that on the way back to Chitral. We passed several lengths of huge ugly piping, part of a failed water project by the Aga Khan charity AKRSP. It cost nine million rupees (£75,000), but was never finished. Another AKRSP project involved building a road, but ‘they put it on the wrong side of the river and it washed away. I’ve seen so much money wasted here, money which could have helped the people in so many good ways.’

When Lines started her UK charity, a lawyer friend told her to read a biography of Dian Fossey, the murdered American ethologist. ‘He told me, “If what you do is not successful you will have no problem, but if you achieve things your life will be miserable.” It’s an observation that has come true.’ Despite her successes – there is hope that Unesco will declare the valleys a heritage site – Lines fears that Kalash culture may disappear entirely within a decade.

Prince Siraj Ulmulk, the owner of the Hindu Kush Heights, a hotel overlooking the Chitral river valley, told me, ‘We’re so lucky someone like Maureen is giving her time to us. We could never understand why someone would leave a lovely place like England to do this. It’s a hell of a lot of work for one person to take on. I just hope she keeps on doing what she’s doing.’

‘I carry on because of the women,’ Lines said. ‘People ask, “What made you give up your life to do this?” What is it I’ve given up? I’m doing exactly what I want to do and the whole way of life here has given me so much. I’ve had a very rich life.’